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Old 09-02-2017, 11:50 AM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
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You're not quite getting it. The phosphate glass is an entirely different formula with similar viscosity and expansion characteristics. As a glass, it will fit both my clear formula and the clear base formula that has a good affinity for color as well.

I have melted Dave's phosphate and it's a very nice glass. It fit my basic portfolio the last time I tried it. Dave is spot on with one thing and that is to replace the calcium with Strontium. It makes what is difficult, easy. If you don't you'll see Apatite crystals everywhere. The only way to avoid hat in a calcum based phosphate is to melt at 2400F or hotter. Even so, I think it could have trouble being melted cold and I did melt it at about 2275F as I recall.

Now you will get an opal glass melting my color formula using silver but it will be a variation on many amber tones, never white. It strikes in many ways similarly to a phosphate which draws from the pot clear and then cooled substantially. Then on reheating the phase separation occurs more in the form of colloidal strands which are big molecules tending to reflect light rather than to allow light to be transmitted. They grow, they collapse, they grow again, always getting a bit fainter and that's pretty much true of any of the crystal/colloidal growth structures in glass.
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